Crawler tractor

ABSTRACT

A crawler tractor comprises steering mechanisms ( 44 ) ( 45 ) for rotating a machine body by causing right and left crawler belts ( 9 ) to move differentially. The tractor is characterized in that the steering mechanism ( 44 ) is connected to a drive system located behind a reverser mechanism ( 21 ) that moves the machine body forward and back. Even when the machine body movement direction is changed from forward to back, the direction of the steering wheel ( 18 ) and the direction of the rotation of the machine body are kept the same, so that a reversed steering phenomenon is prevented from occurring, and an appropriate operation in forward or back movement is enabled with a simple structure that does not require an additional mechanism such as a reverse-steering preventions mechanism.

TECHNICAL FIELD

The present invention relates to a crawler tractor having right and lefttraveling crawlers.

BACKGROUND ART

Conventionally, traveling wheels are generally used for the travelingparts of tractors, but in some cases, traveling crawlers are used (forexample, JP-A 2001-253362). In the conventional art, in case of thatsteering mechanisms such as a reduction gear and a conical linkmechanism are connected to the steering wheel, the reduction gearmechanism and the conical link mechanism are mounted as separate unitsto the steering wheel column. Thereby, a large number of components wererequired, and the assembling operation was not easy but difficult.

DISCLOSURE OF THE INVENTION

According to the present invention, a crawler tractor comprises steeringmechanisms 44, 45 for staring to rotate a machine body by causing rightand left crawler belts 9 to move at differential speed. The steeringmechanism 44 is connected to a driving system at a position locatedbehind a reverser mechanism 21 for switching a moving direction of themachine body to forward or rearward. Thereby, even when the movingdirection of the machine body is changed from forward to rearward, thesteering direction of the steering wheel 18 and the rotating directionof the machine body are kept the same, so that a reversed steeringphenomenon is prevented, and an appropriate operation in forward orrearward movement is enabled with a simple structure not requiring anadditional mechanism such as a reverse-steering prevention mechanism.

Further, the crawler tractor comprises travel speed-change mechanisms22, 23 of gear-switching type for changing travel speed by switching agear train. An input side of the steering mechanism 44 is connected to aspeed-change shaft 33 of the travel speed-change mechanism 22. Thereby,comparing with one in which the speed-change mechanism is directlydriven by the engine 10, the steering mechanism 44 can be disposed withfine heat balance without adversely affecting accessories of the engine10 so as to enable the steering mechanism 44 to be disposedconveniently. Moreover, since the speed change shaft 33 is disposedbehind the reverser mechanism 21, a reversed steering wheel can beprevented and a fine rotating operation with the same rotating radiuscan be obtained irrespective of the speed change operation of a maintravel speed-change mechanism.

Further, the steering mechanism 44 is connected to the steering wheel 18via a reduction gear 101 and a link mechanism 72 which are mounted in acantilever manner to a single stay 102 of a steering wheel column 19.Therefore, it is possible to improve the assembling efficiency bymounting the reduction gear 101 and the link mechanism 72 to the singlestay 102 in a compact and light-weighted manner, and to miniaturize thesteering wheel column 19.

Further, the steering wheel column 19, to which the steering wheel 18and the link mechanism 72 and the like integrally are connected, issupported by the machine body in a vibration-absorbing manner viavibration-absorbing members 107, 108, 109. Thereby, it is possible toprevent the machine body vibration from being transmitted to thesteering wheel 18 so as to enable a stable and fine steering wheeloperation.

Further, the steering mechanism comprises a steering pump 44 and asteering motor 45, and the steering motor 45 is connected to an inputshaft 50 of a differential mechanism 25 of planetary gear type. Thisenables a simple arrangement close to the differential mechanism 25irrespective of the input positions of the steering mechanisms 44, 45,and by making the steering motor 45 and the differential mechanism 25 bein one unit, the assembling operation thereof into the machine body canbe easy.

Further, a control member 73 of the steering mechanism 44 is connectedto the steering wheel 18 via the link mechanism 72, and an auxiliaryspeed-change lever 71 of the travel speed-change mechanism 23 isconnected to the link mechanism 72 so as to adjust operating amount ofthe steering mechanism 44 when the auxiliary speed-change lever 71 isoperated for auxiliary speed change. Thereby, when the travel speed isat a high speed or a low speed, a rotational difference between theright and left traveling crawlers 9 becomes large or small with the linkmechanism 72. This enables rotation in a good feeling with anappropriate rotating radius.

Further, with respect to a certain steering amount of the steering wheel18, the tractor is so set that a rotational difference between the rightand left traveling crawlers 9 becomes large when the auxiliary speedchange is at a high speed, and a rotational difference between the rightand left traveling crawlers 9 becomes small when the auxiliary speedchange is at a low speed. Thereby, it is possible to have a good feelingin rotation by driving the right and left traveling crawlers 9 with anappropriate rotational difference corresponding to the travel speed ofthe auxiliary speed-change operation.

Further, a driving part 2 of traveling crawler belts 9 is disposed at afront side of the machine body and transmission cases 12, 30 having thetravel speed-change mechanisms 22, 23 are disposed at a rear side of themachine body, and the transmission case 30 is provided with a travelbrake 36. Since the brake 36 is disposed to the transmission case at asame position as in a conventional wheel tractor, transmission cases canbe commonly used, so that the size of a transmission bevel gear 35connected to the brake shaft 37 can be set freely. In addition, thenumber of components is reduced since the travel brake 36 is provided toonly one side of the right and left traveling crawlers 9, enabling thestructure to be simplified.

Further, the brake shaft 37 of the travel brake 36 is supported by thetransmission case 12 and a brake case 51, and the differential mechanism25 is provided at the front side of the machine body, and only thetravel brake 36 is provided to the brake case 51 so as to enable therear axle part of the conventional four-wheel transmission structure tobe used effectively. Moreover, it is possible to reduce the number ofcomponents of the travel brake 36, and to reduce the weight byshortening the length of the brake shaft 37.

Further, the brake shaft 37 of the travel brake 36 is supported in thetransmission case 12 in a both ends supported manner. Therefore,irrespective of the mounting position of the brake case 51, it ispossible to assemble the brake shaft 37 and the gear 35 within thetransmission case 12 with fine assembling accuracy, and to improve thereliability by stably keeping the assembling accuracy of the brake shaft37 and the gear 35. Moreover, brake components of wheel tractors can bediverted, and the peripheral speed of a brake plate (friction disc) 52can be lowered, and a rise of the oil temperature can be suppressed byreducing portions, which are dipped into the oil.

Further, the brake case 51 of the travel brake 36 is used as a sidecover of the transmission case 12, and the brake case 51 is used as asupport member for supporting crawler frames 1 on which crawler belts 9are mounted. Thereby it is possible to easily change the vehicle bodywidth such as mounting widths of the right and left traveling crawlerbelts 9 with a simple means of only changing the whole length of thebrake case 51 so as to correspond to the types of vehicle body widths.

Further, step parts 110, 111 where a driving operator gets on and fenderparts 62, 64 are respectively integrated, and provided on right and leftsides separately. Therefore, cover bodies of the step parts 110, 111 andthe fender parts 62, 64 covering both right and left sides of themachine body can be attached or removed easily. Moreover, it is possibleto remove a floor part 112 at the center easily so as to improve themaintainability to perform a good maintenance.

Further, a fuel tank 63 for the engine 10 is mounted to one of right andleft vehicle body frames 113 a, 113 b, to which the steps 110, 111 wherethe driving operator gets on and the fenders 62, 64 are integrallyconnected. This construction enables the fuel tank 63 to be removed ormounted easily from the outside of the machine body. Moreover, it ispossible to conceal the inside of the tank 63 by the fender 62 disposedbetween the driver seat 17 and the fuel tank 63 so as to secure thedriving space in a good condition.

Further, it is possible that the travel speed-change mechanism 188 forchanging travel speed is connected to the driving system at a positionlocated behind the reverser mechanism 21, whereby the travelspeed-change mechanism 188 and the steering mechanism 44 are connectedbehind the reverser mechanism 21 in a compact manner without limitationso as to make the driving system simple.

Further, it is possible that the travel speed-change mechanism 188 andthe steering mechanism 44 are arranged in serial, whereby the travelspeed-change mechanism 188 and the steering mechanism 44 are formed as acompact integrated form so as to enable easy assembling into the machinebody.

Further, the travel speed-change mechanism 189 and the steeringmechanism 45 are connected to the transmission case 2 having thedifferential mechanism 25 of planetary gear type so as to be arrangedopposite each other with the transmission case 2 sandwichedtherebetween, and the travel speed-change mechanism 189 and the steeringmechanism 45 are mounted to the transmission case 2 with a compactintegrated structure, thereby simplifying the machine bodyconfiguration.

Further, it is possible that a fuel tank 190 for the engine 10 isdisposed between the right and left fenders 62 behind the driver seat17, and another fuel tank or fuel tanks 191 are disposed inside one orboth of the right and left fenders 62, whereby the tank capacity isincreased while the machine body width is kept constant and the reservedamount of the fuel is increased in a fine manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall left side view.

FIG. 2 is an overall plan view.

FIG. 3 is an overall right side view.

FIG. 4 is an overall front view.

FIG. 5 is an overall rear view.

FIG. 6 is an overall bottom view.

FIG. 7 is a perspective illustration of a main body.

FIG. 8 is a sectional illustration of the main body.

FIG. 9 is a sectional plan view of the main body.

FIG. 10 is a sectional side view of a transmission case.

FIG. 11 is a sectional plan view of the transmission case.

FIG. 12 is a driving illustration of a steering pump.

FIG. 13 is a sectional plan view of a front transmission case.

FIG. 14 is an illustration of a brake.

FIG. 15 is an illustration of a front safety frame.

FIG. 16 is an illustration of a rear safety frame.

FIG. 17 is a velocity diagram showing a first speed of auxiliary speedchange.

FIG. 18 is a velocity diagram showing a second speed of auxiliary speedchange.

FIG. 19 is a velocity diagram showing a third speed of auxiliary speedchange.

FIG. 20 is an illustration showing an arrangement of a rotation sensor.

FIG. 21 is a front illustration showing the arrangement of the rotationsensor.

FIG. 22 is an illustration showing the relationship between a steeringoperating system and an auxiliary speed-change operating system.

FIG. 23 is an illustration of a conical link mechanism.

FIG. 24 is an illustration of a steering wheel column.

FIG. 25 is a side illustration of the steering wheel column.

FIG. 26 is a rear illustration of the steering wheel column.

FIG. 27 is an illustration of a case.

FIG. 28 is an illustration of an L-shaped stay.

FIG. 29 is a diagram showing the relationship between the auxiliaryspeed change and a steering wheel angle.

FIG. 30 is a diagram showing the relationship between a vehicle speed atthe first speed of the auxiliary speed change and a steering wheelangle.

FIG. 31 is a plan illustration of steps.

FIG. 32 is a side illustration of the step.

FIG. 33 is an integrated illustration of the steps and fenders.

FIG. 34 is a plan illustration of a foot placing part.

FIG. 35 is sectional illustration of the foot placing part.

FIG. 36 is an illustration showing an exemplary opening/closingstructure of the foot placing part.

FIG. 37 is an illustration showing an exemplary opening/closingstructure of the foot placing part.

FIG. 38 is an illustration showing an exemplary opening/closingstructure of the foot placing part.

FIG. 39 is an illustration of a fuel tank.

FIG. 40 is a side illustration of a crawler.

FIG. 41 is a plan illustration of the crawler.

FIG. 42 is an illustration showing an exemplary modified structure of abrake shaft support.

FIG. 43 is an illustration showing an exemplary modified structure ofthe brake shaft support.

FIG. 44 is an illustration showing mounting of a first transmissionshaft.

FIG. 45 is a rear illustration showing the mounting of the firsttransmission shaft.

FIG. 46 is an illustration showing a modification of a keep plate.

FIG. 47 is a hydraulic circuit diagram.

FIG. 48 is a hydraulic circuit diagram.

FIG. 49 is a side illustration of a hydraulic conduit.

FIG. 50 is a side illustration of a reverser lever.

FIG. 51 is an illustration showing mounting of steering and travelpumps.

FIG. 52 is an illustration showing mounting of steering and travelmotors.

FIG. 53 is a plan illustration of a tank.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described indetail with reference to the drawings. FIG. 1 is a left side view of acrawler tractor, FIG. 2 is a plan view of the same, FIG. 3 is a rightside view of the same, FIG. 4 is a front view of the same, FIG. 5 is arear view of the same, FIG. 6 is a bottom view of the same, and FIG. 7is a perspective illustration of a vehicle body. In this embodiment, afront transmission case 2 is fixed to the front parts of a pair of rightand left square barrel-shaped crawler frames 1, and right and leftdriving sprockets 4 are pivotally supported on right and left axles 3 ofthe front transmission case 2. Further, tension rollers 6 are mounted onthe rear parts of the crawler frames 1 via tension frames 5, andtraveling crawlers 9 are rolled between the driving sprockets 4 and thetension rollers 6 via equalizer rotating wheels 7 and idlers 8, so thata pair of right and left traveling crawler belts 9 are mounted.

Between the right and left crawler frames 1, an engine 10 is mountedabove the front side, and the outside of the engine 10 is covered with abonnet 11. Further, between the right and left crawler frames 1, a reartransmission case 12 is provided in the rear side thereof. The reartransmission case 12 is provided with a hydraulic hoist cylinder 14 witha lift arm 13, a top link 15 and a lower link 16. Farm working machinerysuch as a tillage rotary working machine or a plow is provided to thelinks 15 and 16 in a freely lifted/lowered and detachable manner so asto perform a tilling operation in a farm field or the like.

Further, a driver seat 17 is placed above the rear transmission case 12behind the bonnet 11, and a steering wheel column 19 with a circularsteering wheel 18 and a braking pedal 20 are mounted at the front of thedriver seat 17.

As shown in FIGS. 8 to 10, axles 3 of the right and left travelingcrawlers 9 are connected to the output shaft of the engine 10 via aforward/rearward switching mechanism 21, a main speed change gear shiftmechanism 22, an auxiliary speed change gear shift mechanism 23, atravel transmission shaft 24 and a forced differential mechanism 25, soas to move the machine body. Further, a PTO output shaft 29 protrudedrearward from the rear transmission case 12 is connected to aforward/rearward output shaft 26 of the forward/rearward switchingmechanism 21 via a PTO clutch 27 and a PTO speed change gear shiftmechanism 28, so as to transmit power to a farm working machine providedto the rear of the machine body.

Further, in a power transmission case 30 between the rear transmissioncase 12 and the engine 10, the forward/rearward switching mechanism 21and the gear shift mechanism 22 for main speed change are accommodated,and the input shaft 31 of the forward/rearward switching mechanism 21 isconnected to the output shaft of the engine 10 via a dumper 32, whilethe main speed-change shaft 33 of the main gear shift mechanism 22 isconnected to the forward/rearward output shaft 26 of theforward/rearward switching mechanism 21.

Further, the auxiliary speed change gear shift mechanism 23 and the PTOspeed change gear shift mechanism 28 are provided at front side and rearside of the rear transmission case 12, and an auxiliary speed changeshaft 34 of the auxiliary speed change gear shift mechanism 23 isconnected to the main speed change shaft 33, and a brake shaft 37 of thetravel brake 36 is connected to the rear end of the auxiliary speedchange shaft 34 via a pair of bevel gears 35, and the rear end of atravel transmission shaft 24 is connected to the front end of theauxiliary speed change shaft 34 via an intermediate shaft 38.

As shown in FIGS. 9 and 13, the front transmission case 2 accommodatesthe forced differential mechanism 25 with right and left planetary gearmechanisms 39 therein, and the right and left planetary gear mechanisms39 are connected to the front end of the travel transmission shaft 24via a differential input shaft 40, a bevel gear 41 and a planetary gearinput shaft 42. A travel speed-change output from the traveltransmission shaft 24 is transmitted to the right and left axles 3 viathe right and left planetary gear mechanisms 39 and the planetary gearoutput shaft 43, whereby the right and left traveling crawlers 9 aredriven at a substantially same speed and in the same direction so as totravel forward or rearward.

Further, a hydraulic steering pump 44 and a hydraulic steering motor 45of the hydrostatic transmission (HST) for steering to rotate the machinebody are arranged separately. The steering pump 44 is placed in parallelto the right outer side of the transmission case 30, and a pump shaft 47of the steering pump 34 is connected to the front end of the mainspeed-change shaft 33 via a set of three transmission gears 46 so as toinput power after the main speed-change into the pump shaft 47. Thehydraulic steering motor 45 is fixed to the front face of the fronttransmission case 2, and the motor shaft 48 of the steering motor 45 isconnected to the right and left planetary gear mechanisms 39 via theright-and-left-reversed bevel gear 49 and the right and left gear shafts50 to thereby transmit the steering output, the speed of which isnon-stepwisely changed by the pump 34 and the motor 45, to the wheels 3via the right and left planetary gear mechanisms 39. As shown in FIGS.17, 18 and 19, the right and left traveling crawlers 9 are driven at asubstantially constant speed and a rotational difference between theright and left crawlers 9 are made to be proportional to the travelingspeed of the speed stage (first speed to fourth speed) of the main speedchange, so that even when the speed stage (first speed to fourth speed)of the main speed change is switched, the machine body is rotated in aright or left direction with the same rotating radius. Note that sincethe steering pump 34 and the auxiliary speed change gear shift mechanism23 are not interlocked with each other, when the speed stage (firstspeed to third speed) of the auxiliary speed change is changed, therotating radius is also changed as shown in FIGS. 17 to 19. As the speedstage of the auxiliary speed change is smaller (third speed>secondspeed>first speed), the rotating radius becomes smaller, so that quickoperating feeling can be achieved. Further, in the auxiliary speed stagewith pivot turn (first stage, second stage) as shown in FIGS. 17 and 18,pivot turn is performed at the same steering wheel angle irrespective ofthe speed stage of the main speed change.

As obvious from the above, in the crawler tractor having the hydraulicsteering pump 44 and the hydraulic steering motor 45 which are of theHST for steering to rotate the machine body, the steering pump 44 isconnected to a driving system at a position located behind theforward/rearward switching mechanism 21 which is a reverser mechanismfor moving the machine body forward and rearward, whereby even when themachine body is changed from moving forward to rearward, the operationaldirection of the steering wheel 18 and the rotating direction of themachine body are kept the same, so that a reversed steering phenomenonis prevented. This enables an appropriate operation in forward orrearward movement with a simple structure, which does not need anadditional mechanism such as a reverse-steering prevention mechanism.

Further, the HST for steering is divided into the variable displacementpump 44 and the fixed displacement motor 45, and the fixed displacementmotor 45 is connected to the gear shaft 50 which is the input shaft ofthe planetary gear-type differential mechanism 25 so as to enable asimple arrangement in which the motor 45 is placed close to thedifferential mechanism 25 not relating to the input position of the pump44, and the fixed displacement motor 45 and the differential mechanism25 are made to form one unit, so that they can be incorporated into themachine body easily.

Further, the variable displacement pump 44 of the HST for steering isarranged in parallel with the transmission case 30, and the pump 44 isplaced in the vicinity of the engine driving system and the motor 45 isplaced in the vicinity of the differential mechanism 25 separately,whereby a suitable arrangement with no limitation caused by theirpositions can be achieved. In addition, this also enables to make themachine body smaller by incorporating the pump 44 in a good conditionin, for example, in a free space between the transmission case 30 andthe traveling crawler 9.

Further, the driving portion of the steering pump 44 is connected to themain speed-change shaft 33 of the travel speed-change mechanism 22,whereby the steering pump 44 is mounted with fine heat balance withoutadversely affecting accessories of the engine, comparing with one inwhich the speed-change mechanism is directly driven by the engine 10.Further, the main speed-change shaft 33 is placed behind the switchingmechanism 21 so as to prevent a reversed steering and to enable finerotating operation with the same rotating radius irrespective of changesin speed of the main speed change.

As shown in FIGS. 11, 12 and 14, right and left brake cases 51, commonlyused for the right and left, are fixed to both of the right and leftsides of the rear transmission case 12, and the travel brake 36 isaccommodated in the left brake case 51 of either right or left side. Abrake arm 55 of a brake cum 54 for braking a brake plate 52 by pressinga brake press plate 53 is connected to the braking pedal 20 via firstand second brake rods 55 a and 55 b, and when the travel brake 36 isbraked by the braking pedal 20, both operations of traveling forward andsteering to rotate are stopped. Further, transmission case and brakecase of a conventional wheel tractor are used as the rear transmissioncase 12 and the brake case 51, and since the brake shaft 37 is connecteddirectly to the auxiliary speed change shaft 34 which is the final shaftvia the bevel gear 35, free setting of the bevel gear 35 is enabled, andthe mounting number of brake plates 52 is reduced effectively.

Further, right and left crawler supporting frames 56 connected to thecrawler frames 1 are fixed on the outside faces of the right and leftbrake cases 51, and by replacing the brake cases 51 of different rightand left lengths, the gap between the right and left traveling crawlers9 can be changed easily, so as to increase the adaptability to bodywidth types.

As obvious from the above, the front transmission case 2 which is thetravel driving part of the right and left crawlers 9 is disposed at thefront side of the machine body, while the rear transmission cases 12 andthe transmission case 30 with the travel speed-change mechanisms 22, 23are disposed at the rear side of the machine body, and the travel brake36 is placed between the transmission case 30 and the tension roller 6which is a rotation wheel of one of the right and left crawlers 9, andthe brake 36 is connected to the transmission case at a same position asthat in a conventional wheel tractor so as to enable the transmissioncase and the like to be commonly used. This enables the size of thetransmission bevel gear 35 connected to the brake shaft 37 to be setfreely, and to reduce the number of components due to the arrangement ofone side of the right and left crawlers 9 so as to simplify thestructure.

Further, a side cover of the rear transmission case 12 is used as abrake case 51 of the travel brake 36, and the brake case 51 is used as asupporting member of the crawler frame 1, whereby the vehicle body widthsuch as the widths of the right and left crawlers are changed easilywith an easy means of just changing the whole length of the brake case51 so as to be well adaptable to the types of the vehicle body width.

As shown in FIGS. 1, 15 and 16, the tractor is so configured that portalfront and rear safety frames 57, 58 are respectively placed at aposition in front of the steering wheel column 19 and at a positionbehind the driver seat 17, and the lower ends of the front safety frames57 are fixed detachably via mounting members 60 to yoke frames 59connecting the front transmission case 2 and the crawler frames 1, andthe lower ends of the rear safety frames 58 are fixed detachably viamounting members 61 to the right and left supporting frames 56, wherebythe front and rear safety frames 57 and 58 are supported by the crawlerframes 1 with a simple structure and fine strength.

As shown in FIG. 16, the tractor is so configured that a fuel tank 63for the engine 10 is disposed outside the left fender 62, and a battery65 is disposed within the right fender 64, respectively, to therebyobtain a good right and left balance of the machine body with the fueltank 63 and the battery 65 placed on the opposite side in the right andleft direction. Further, covers 66 are mounted in a openable/closablemanner via fulcrum shafts 67 on the outside of the right and leftfenders 64 so as to improve stable holding and maintainability of thebattery 65.

Further, the tractor is so configured that the vehicle speed is detectedfrom rotation of the travel transmission shaft 24, and as shown in FIGS.20 and 21, a shaft rotation sensor 70 is mounted to a shaft case 68 ofthe travel transmission shaft 24 via a sensor case 69, and the vehiclespeed is computed based on the rotation of the transmission shaft 24detected by the rotation sensor 70 and is displayed on the drive panellocated above the steering wheel column 19.

As shown in FIGS. 22 to 28, an auxiliary speed change lever 71 of theauxiliary speed change gear shift mechanism 23 is connected to aspeed-change arm 73 of the steering pump 44 via a conical link mechanism72. A steering input shaft 77 is connected to the steering wheel shaft74 of the steering wheel 18 via a small radius gear 75 and a sector gear76, and an input fulcrum shaft 78 is connected to the lower end of thesteering input shaft 77 via a universal joint, and a steering inputmember 79 is fixed to the input fulcrum shaft 78, and the steering inputmember 79 is mounted rotatably to a second end of a horizontal speedchange input shaft 81, a first end of which is supported rotatably by abearing member 80 in a cantilever manner, and the steering input member79 is supported so as to freely rotate about the steering input shaft77. With a normal or reverse rotation of the steering input shaft 77,the steering input member 79 is rotated in a normal or reverse directionabout the axis line of the substantially vertical input shaft 77, andwith a normal or reverse rotation of the speed change input shaft 81,the input fulcrum shaft 78 and the steering input member 79 are rotatedin a slanting state in one direction about the axis line of the inputshaft 81 which is substantially horizontal in the right and leftdirection. To an intersection point where the axis line of the steeringinput shaft 77 in the vertical direction and the axis line of the speedchange input shaft 81 in the right and left horizontal direction crossat a right angle, the connecting portion of the universal joint for therespective shafts 77 and 78 are mounted. With an operation of thesteering wheel 18 to rotate the steering input shaft 77 in the normal orreverse direction, the steering input member 79 is rotated in the normalor reverse direction about the axis line of the steering input shaft 77.

Further, an auxiliary speed-change operational shaft 82 is pivotedrotatably on the lower rear side of the steering wheel column 19, andthe left side end of the auxiliary speed-change operational shaft 82which is laterally mounted in substantially horizontal in the right andleft direction is connected to the auxiliary speed-change lever 71 via aspeed-change link 83 and a rod 84. With the speed change operation ofthe auxiliary speed-change lever 71 in the back and forth direction, theauxiliary speed-change operation shaft 82 is rotated in the normal orreverse direction. The auxiliary speed-change operation shaft 82 isconnected to the speed-change input shaft 81 via a rod-shaped auxiliaryspeed-change member 85 and a lower link 86. With an operation of theauxiliary speed-change operation shaft 82 in the normal or reversedirection by the auxiliary speed-change lever 71, the input fulcrumshaft 78 is rotated in a slanting state in one direction about the axisline of the speed-change input shaft 81.

Further, a steering output shaft 87 of cylinder shaft shape is mountedrotatably to a steering operation shaft 88, and a steering output member89 of link type is fixed to the steering output shaft 87, and the upperend of a rod-shaped steering connecting member 90 is connected to thesteering input member 79 via a steering input connecting part 91 ofuniversal joint type, and the lower end of the steering connectingmember 90 is connected to the steering output member 89 via a steeringoutput connecting part 92 of ball joint type, whereby the conical linkmechanism 72 for changing the travel route is configured.

Further, the speed-change arm 73 of the steering pump 44 is connected tothe steering output shaft 87 via a steering link 93 and via a steeringoutput rod 94. By operating the speed-change arm 73 in the normal orreverse direction, the swash plate angle of the steering pump 44 isadjusted so as to perform of controlling a rotational number andswitching between normal rotation and reverse rotation of the steeringmotor 45 to thereby perform non-stepwise change of the steering angle(rotational radius) and switching of a right and left steeringdirection.

Then, as shown in FIGS. 29 and 30, the tractor is so configured that theinput fulcrum shaft 78 (bottom face angle α of the bottom face 72 a ofthe conical link mechanism 72) is so set as to be tilted to the largest(α is nearly equal 26°) when the auxiliary speed-change lever 71 is atthe highest speed (third speed), and tilted to the smallest (α is nearlyequal 10°) at the lowest speed (first speed). With this configuration,at the same steering wheel angle of the steering wheel 18, therotational difference between the right and left traveling crawlers 9becomes larger than the standard when the auxiliary speed change is atthe highest speed, and it becomes smaller than the standard at thelowest speed so as to cause changing-direction of the vehicle (orturning of the vehicle) at the low speed to be gentle in the state whilethe rotational radius at the highest speed is maintained (small), tothereby provide good operational feeling both at the highest speed orthe lowest speed of the auxiliary speed change. Note that the referencenumeral 95 in FIG. 22 is a main speed-change lever for performingspeed-change operation of the main speed change gear shift mechanism 22in a range from the first speed to the fourth speed.

As obvious from the above, the steering pump 44 is connected to thesteering wheel 18 via the conical link mechanism 72 and the auxiliaryspeed-change lever 71 of the travel speed-change mechanism 23 isconnected to the conical link mechanism 72, whereby the operating amountof the steering pump 44 is adjusted when the auxiliary speed-changelever 71 is operated, so that when the traveling speed is high or low,the rotational difference between the right and left traveling crawlers9 is made to be large or small by the conical link mechanism 72,respectively, so as to enable changing-direction of the vehicle with agood feeling in which the rotational radius is appropriate. With respectto a certain steering amount of the steering wheel 18, the rotationaldifference between the right and left traveling crawlers 9 is set to belarge when the auxiliary speed change is at a high speed, and therotational difference between the right and left traveling crawlers 9 isset to be small when the auxiliary speed change is at a low speed, andthe right and left traveling crawlers 9 are driven with an appropriaterotational difference corresponding to the traveling speed of theauxiliary speed-change operation so as to provide good feeling inchanging-direction (or turning).

Further, a reverser lever 96 is mounted on the left side of the steeringwheel 18, so that a reverser valve 99 for switching on/off hydraulicmultiple-disc forward/rearward clutches 97 and 98 of theforward/rearward switching mechanism 21 is switch-operated by the lever96, and an acceleration lever 100 is protrudingly formed on the rightside of the steering column 19.

As shown in FIGS. 25 to 28, a steering reduction gear mechanism 101,formed of the small diameter gear 75, the sector gear 76 and the like,and the conical link mechanism 72 are mounted to a single stay 102 ofthe steering column 19. The upper part of the stay 102 is formed to be abox-shaped case 103, and a steeling wheel shaft cylinder 106 is fixed tothe upper side plate 103 a of the case 103 with bolts 105, and thereduction gear mechanism 101 is accommodated inside the case 103. Thelower side of the stay 102 is formed to be an L-shaped stay 104 with thefront face part 104 a and the right face part 104 b, and the conicallink mechanism 72 such as the operation shaft 82, the output shaft 87and the bearing member 80 are supported on the right face part 104 b ina cantilever manner.

Further, the tractor is so configured that a steering mounting plate106, which is fixed detachably to the stay 102 with the bolts 105, andthe stay 102 are integrally supported in a vibration-absorbing manner bythe engine 10 and the transmission case 30. On the rear face of theengine 10, the front face of the mounting plate 106 is mounted via avibration-absorbing member 107 such as a vibration-absorbing rubber, andon the front upper face of the transmission case 30, the mounting plate106 and the mounting plate 102 a for the operation shaft 82 of the stay102 are supported via vibration-absorbing members 108, 109 such asvibration-absorbing rubbers, so that the stay 102, the mounting plate106 and the like are supported integrally with the steering wheel 18 ina vibration-proof manner by the machine body to thereby preventvibration from being transmitted to the steering wheel 18 and the like.Further, the respective parts of the steering wheel column 19 such asthe stay 102 and the mounting plate 106 are made to be able to bediscomposed easily so as to improve maintainability.

As obvious from the above, a non-stepwise speed-change mechanism 170 forsteering is connected to the steering wheel 18 via the reduction gear101 and the conical link mechanism 72, and the reduction gear 101 andthe conical link mechanism 72 are mounted to the signal stay 102 of thesteering wheel column 19 in a cantilever manner, whereby the reductiongear 101 and the conical link mechanism 72 are mounted to the signalstay 102 in a compact and light weighted manner so as to improve theassembling operation and to miniaturize the steering wheel column 19.

Further, since the steering wheel column 19 to which the steering wheel18 and the conical link mechanism 72 are mounted integrally is supportedby the machine body in a vibration-absorbing manner via thevibration-absorbing members 107, 108, 109, it is possible to prevent themachine body vibration from being transmitted to the steering wheel 18so as to enable stable and good steering wheel operation.

As shown in FIGS. 31 to 35, the tractor is so configured that the rightand left driving steps 110, 111 where a driving operator gets on at thefront side of the driver seat 17, and the right and left fenders 62, 64on the right and left sides of the driver seat 17 are integratedrespectively. And the integrated units are disposed at right and leftseparately. A central floor 112 is placed at the front side of thedriver seat 17, and the right and left steps 110, 111 are locatedrespectively on the right and left sides of the central floor 112. Themounting members 60 are fixed to the front ends of the right and leftsteps 110, 111, and the rear ends of the right and left steps 110, 111are fixed to the right and left vehicle body frames 113 a, 113 b in theback and forth direction, and the right and left fenders 62 and 64 areconnected to the rear upper faces of the right and left vehicle bodyframes 113 a, 113 b, and the mounting members 61 are connected to therear lower faces of the right and left vehicle body frames 113 a, 113 b.And the integrated units, which are formed the right and left drivingsteps 110, 111 and the right and left fenders 62, 64, respectively, areconnected to and supported by the crawler frames 1 via the respectiveframes 59, 56 at a front side and a rear side of the integrated units.

Further, concaved portions 114 recessed downward by a certain length areformed in the inner step parts 110 a, 111 a of the steps 110, 111, andinspection openings 115 are formed in the concaved portions 114. On theupper faces of the concaved portions 114, foot steps 118 are elasticallysupported via a number of vibration-absorbing members 116 such asvibration-absorbing rubbers and flat head pins 117. The foot steps 118are removed by detaching stopping pins 119 engaged with the lower endsof the flat head pins 117 so as to enable respective parts such as rods84 disposed below the steps 110 a and 111 a to be inspected easily. Notethat the reference numeral 120 is a mat provided on the upper face ofeach of the steps 110 and 111, the floor 112 and the foot steps 118.

As shown in FIGS. 36 to 38, the foot steps 118 may be so configured asto be openable in a state where they are not removed from the right andleft step parts 110 a, 111 a. The tractor shown in FIGS. 36 and 37 is soconfigured that the right and left foot steps 118 are connected suchthat the inner sides thereof are openable/closable via hinges 121 on theright and left sides of the central floor 112, and the outer sidesthereof are locked to closing plates 123 provided in a horizontallyrotatable manner to the right and left steps 110, 111 via locking pins122 so as to always keep the foot steps 118 in the closed state, andwhen the closing plates 123 are unlocked, the foot steps 118 can beopened easily.

Further, the tractor shown in FIG. 38 is so configured that the rightand left foot steps 118 are connected to each other so as to form anintegrated foot step 124. The rear side of the foot step 124 isconnected in an openable/closable manner to the inner step parts 110 aand 111 a via the hinges 121, and locking members 125 fixed to the frontside of the foot step 124 are connected detachably to locking plates 126of the inner step parts 110 a and 111 a with locking pins 127 so as toenable the foot step 124 in which the right and left steps and thecentral floor are integrated to be opened easily. This makes maintenanceand inspection of the front lower side of the driver seat 17 easy.

As obvious from the above, the steps 110, 111 which are the step partswhere the driving operator gets on and the fenders 62, 64 which arefender parts are integrally formed on the right and left sidesseparately. This enables cover bodies of the steps 110, 111 and thefenders 62, 64, largely covering the right and left sides of the machinebody, to be attached and disassembled easily, and also enables to removeonly the floor 112 which is the central floor part so as to improvemaintainability and obtain a good maintenance.

Further, since the right and left steps 110 and 111 are connected to thecentral floor 112 in an openable/closable manner, it is possible toprevent inconvenience such as falling off of the right and left steps110 and 111, and to surely keep the positions of the steps 110 and 111and make open/close easily.

Further, since the foot steps 118 which are the foot step parts of theright and left steps 110 and 111 have a vibration-absorbing structure,it is possible to prevent vibration from being transmitted to thedriving operator through the feet to thereby obtain good drivingoperability, and to improve maintainability by enabling the foot steps118 to be removed solely.

As shown in FIGS. 32 and 39, tank supporting members 128, 129 are fixedby welding to the front and rear lower sides of the fuel tank 63, andthe tank supporting members 128, 129 are fixed with bolts 132 to a frontconnecting frame 130 between the step 110 and the vehicle body frame 113a and to the rear connecting frame 131 at the rear end of the vehiclebody frame 113 a. The left fender 62 is fixed to the rear upper face ofthe vehicle body frame 113 a via a mount 133, and a handle 134 placed onthe left fender 62 and a mount 135 fixed to the upper part of the fueltank 63 are fixed by being clamped together to the left fender 62 with abolt 136, whereby the fuel tank 63 is mounted safely and securely at aposition outside the left fender 62.

As obvious from the above, since the fuel tank 63 of the engine 10 ismounted to one of the right and left vehicle body frames 113 a and 113 bwhich integrally connect the steps 110 and 111 where the drivingoperator gets on and the fenders 62 and 64, it is possible to easilyremove or mount the fuel tank 63 positioned from the outside of themachine body, and to secure the driving space in a good condition byconcealing the inner side of the tank 63 with the fender 62 placedbetween the driver seat 17 and the fuel tank 63.

Further, since the upper part of the fuel tank 63 is fixed with the bolt136, which is a member for clamping together, to the handle 134 placedon the upper part of the fender 62 and to the fender 62, it is possibleto fix the upper part of the fuel tank 63 to the fender 62 and thehandle 134 easily so as to fix the position of the fuel tank securelywhile reducing vibration.

Further, since the lower part of the fuel tank 63 is removably fixed tothe tank supporting member 129 fixedly mounted to the vehicle body frame113 a, the lower part of the fuel tank 63 can be supported securely bythe vehicle body frame 113 a so as to improve the stability in mountingthe fuel tank.

As shown in FIGS. 9, 40 and 41, the tractor is so configured thatmounting parts of the crawler frame 1 to the main body is divided intothe front part and the rear part so as to have a front frame 137 of thecrawler frame 1 connected to the front yoke frame 59 and a rear frame138 of the crawler frame 1 connected to the rear yoke frame 56. The rearframe 138 is connected to the front frame 137 such that the front andrear connecting positions are adjustable via bolt long holes 140 formedin the connecting board 139 at the rear end of the front frame 137 andwith bolts 141 so as to compensate welding distortion of the crawlerframe 1 to thereby enable the crawler frame 1 to be connected to themain machine body with fine accuracy.

As shown in FIG. 14, the tractor is so configured that the brake shaft37 of the travel brake 36 is supported in a both sides supported mannerby the rear transmission case 12 and the brake case 51 fixedly mountedto the rear transmission case 12. And the brake shaft 37 is soconfigured to be supported between a partition wall 142 formed on theintermediate inner side of the brake case 51 and a left outside wall 43of the rear transmission case 12. This configuration enables the brakeshaft 37 to be shortened, and thereby decreased the weight.

Further, the tractor is so configured that by adjusting the gear ratioof the bevel gear 35 of the auxiliary speed-change shaft 34, thetransmission torque is reduced so as to make the number of the brakeplates 52 minimum (one).

Further, the tractor shown in FIG. 42 is so configured that a sidewall144 is formed at the outside end of the brake case 51, and the brakeshaft 37 with a long shaft length is supported in a both sides supportedmanner between the left outside wall 143 of the rear transmission case12 and the sidewall 144 so as to stable the support of the brake shaft37.

Further, the tractor shown in FIG. 43 is so configured that the rightand left sidewalls 143 and 146 are formed in a bevel gear room 145 ofthe rear transmission case 12 and the brake shaft 37 is supported in aboth sides supported manner between the right and left sidewalls 143 and146 so as to perform highly accurate mounting of the brake shaft 37 onlyto the rear transmission case 12 not relating to the brake case 51 tothereby improve reliability.

As obvious from the above, the gear type speed-change mechanism 23 forchanging travel speed is provided in the rear transmission case 12 thatis the rear speed-change case, and the brake case 51 that is the rearacceleration part of the rear transmission case 12 accommodates only thetravel brake 36 which is a braking mechanism. And the brake shaft 37 ofthe brake 36 is supported by the rear transmission case 12 and the brakecase 51. Thereby, the differential mechanism 25 is disposed at the frontaxle part and only the brake 36 is disposed at the rear axle part 51 soas to enable the conventional rear axle part to be used effectively.Moreover, it is possible to reduce the number of components of the brake36 and to shorten the length of the brake shaft 37 so as to reduce theweight.

Further, since the brake shaft 37 of the brake 36 is supported withinthe rear transmission case 12 in a both sides supported manner, it ispossible to assemble the brake shaft 37 and the gear 35 in the reartransmission case 12 in accurate assembling so as to stably keep theassembling accuracy of the brake shaft 37 and the gear 35 and to improvethe reliability, irrespective of the mounting of the rear axle part 51such as the brake case 51.

As shown in FIGS. 20, 44 and 45, output of the auxiliary speed changegear shift mechanism 23 is transmitted to the travel transmission shaft24 via a gear 147 of an intermediate shaft 38, a gear 149 of a firsttransmission shaft 148 and a gear 151 of a second transmission shaft150. The first and second transmission shafts 148 and 150 are supportedby a gear case 152 within which the gears 149 and 151 are accommodated,and the gear case 152 is fixed to the transmission case 30 removablywith bolts 153. The first transmission shaft 148 is so configured that alarge diameter part 148 a at a first end passes through one sidewall ofthe gear case 152 and is fixed to the speed-change case 152 by a pin 154with an O-ring 155 being interposed between the speed-change case 152and the large diameter part 148 a, and a small diameter part 148 b at asecond end is fitted to a cover body 156 which inserts into a sidewallof the second side of the gear case 152 with an O-ring 155 beinginterposed between the cover body 156 and the gear case 152. Aring-shaped engagement groove 157 is formed in the outside of the coverbody 156. A keep plate 158 engaging with the engagement groove 157 isfixed to the gear case 152 with a bolt 159, and the transmission shaft148 and the cover body 156 are positioned and held coaxially by the pin154 and the keep plate 158 while the gear 149 is supported rotatably atalmost center of the transmission shaft 148 via bearings 160.

Note that fitting holes 161 and 162 for the transmission shaft 148 andthe cover body 156 formed in the gear case 152 are formed to have thesame diameter so as to achieve fine processability of the gear case 152.

Further, a closing cover 165 is fitted to a fitting hole 164 of a shaftbearing 163 in the opposite side of the gear case 152 through which thetip end of the second transmission shaft 150 protrudes, and aring-shaped engagement groove 166 is formed in the outside the closingcover 165. A keep plate 167 for engaging with the engagement groove 166is fixed to the gear case 152 with a bolt 168 so as to securely closethe opening in the gear case 152 on the opposite side of the tip end ofthe second transmission shaft 150.

Further, as shown in FIG. 46, the keep plates 158 and 167 for the coverbody 156 and the cover 165 may be formed integrally so as to be a singlekeep plate 169.

As obvious from the above, there is provided the gear case 152 which isa transmission case for transmitting power from the intermediate shaft38, which is an output shaft of the transmission case 30 which is adriving case, to the transmission shaft 24 which is a power transmissionshaft via the transmission shaft 148 which is an intermediate shaft, andthe transmission shaft 148 is mounted to the gear case 152 removably inits axial direction with the O-ring 155 being interposed therebetween.Thereby, it is possible to improve workability by assembling thetransmission shaft 148 easily with fine accuracy through a simpleoperation of just inserting the transmission shaft 148 into the gearcase 152, and to make the assembly easier by eliminating the use of anoil seal.

Further, a first end of the transmission shaft 148 is fitted into thegear case 152 and a second end of the transmission shaft 148 is fittedinto the cover body 156 which is a shaft cover inserted into the gearcase. Therefore, the fitting holes 161, 162 of the gear case 152 intowhich the transmission shaft 148 and the cover body 156 are fitted havethe same diameter, whereby it is possible to have the gear case 152 of asimple shape and to improve the processability of the case 152.

Further, the transmission shaft 148 is positioned and fixed to the gearcase 152 with the insertion pin 154, and the cover body 156 ispositioned and fixed to the gear case 152 via the keep plate 158 whichis a regulating plate. This enables an easy attachment/detachment of thetransmission shaft 148 by an easy attachment/detachment of the plate 158without a burden of positioning and fixing the transmission shaft 148 byusing a C-shaped retaining ring or the like so as to improvemaintainability.

As shown in FIGS. 47 to 49, the tractor is so configured that ahydrostatic transmission 170 (HST) for steering, formed of the hydraulicpump 44 and the hydraulic motor 45 for steering the machine body, and acharge pump 171 for supplying hydraulic pressure to the forward andrearward clutches 97, 98 are operatively connected to the engine 10, andoil in the rear transmission case 12 is supplied to the charge pump 171through two, right and left filters 172 placed below the right and leftsides of the rear transmission case 12, and the charge pump 171 isconnected to a steering valve 173 switched by manual operation of thesteering handle 18 and a relief valve 174 for charging the hydraulicpump and a switching valve 175 for main clutch of straight input systemvia the filter 172 a and a hydraulic high pressure circuit 176 so as toutilize the relief pressure of charging (17 to 23 kg/cm²) of the HST 170for steering as an operating pressure of the forward/rearward switchingmechanism 21 (forward/rearward power shift). Further, a servo operatingpressure (17 to 23 kg/cm²) of the controlling oil of the HST 170 is alsostably kept by using the relief valve 174 of the HST 170.

Further, the tractor is so configured that the high-pressure circuit 176is fluidly connected with the forward and rearward clutches 97, 98 viathe switching valve 175, an electromagnetic proportional valve 177 andthe reverser valve 99, and a drain circuit 178 of the steering pump 44and the steering motor 45 is fluidly connected with the hydrauliclubricating parts of the forward and rearward clutches 97 and 98 via anoil cooler 179 and a cooling circuit 180, so as to secure enough amountof oil required for lubricating and cooling the hydraulic multi-discforward/rearward clutches 97 and 98 from the oil leaked from the reliefvalve 174 and the motor 45. The oil leaked from the relief valve 184 andthe motor 45 is flown within a pump housing 181 and a motor housing 182so as to be used for cooling them while the oil leaked from the reliefvalve 174 and the motor 45 combined, and then cooled by the oil cooler179 is supplied to the forward/rearward clutches 97 and 98 so as to beused for lubricating and cooling.

Further, there is provided a relief valve 183 (2 to 3 kg/cm²) forbypassing the oil cooler 179 when the back pressure side of the oilcooler 179 becomes high such as at the time of low temperature, so as toprevent pressure within respective housings 181, 182 from being risenand to prevent oil leakage from the seals and inefficiency. Note thatthe relief valve 183 is placed on the side face of the rear transmissioncase 12 so as to simplify the piping structure by returning the returnedoil from the relief valve 183 into the case 12.

As shown in FIGS. 48 and 49, the tractor is so configured that the rightand left filters 172 are placed below the right and left brake cases 51,and the filter 172 a is disposed below the right side of the bonnet 11so as to enable replacement operation of the filters 172, 172 a easy.Further, the filter 172 is connected to the rear transmission case 12and the filter 172 a is connected to the steering pump 44 in a follow-upmanner so as to obtain an easy conduit arrangement.

As obvious from the above, there are provided the hydraulicforward/rearward switching mechanism 21 for switching forward/rearwardtravel direction of the machine body and the HST 170 for steering torotate of turn the machine body, and a relief oil pressure of thecharging relief valve 174 for the HST 170 for steering is used as anoperational pressure of the hydraulic forward/rearward switchingmechanism 21, whereby operation of the forward/rearward switchingmechanism 21 is performed by using the charge pump 171 for the HST 170for steering so that the hydraulic conduit arrangement system issimplified.

Further, there is provided the cooling circuit 180 for switchingmechanism in which the leaked oil from the charging relief valve 174 andthe leaked oil from the HST 170 for steering are combined to be suppliedto the forward/rearward switching mechanism 21 and cool it, whereby itis possible to secure enough amount of oil required for cooling theforward/rearward switching mechanism 21 by using leaked oil from thedrain circuit 178 of the HST 170 for steering, so that the performancecan be stably kept and the conduit arrangement can be simplified.

Further, the oil cooler 179 for cooling oil supplied to theforward/rearward switching mechanism 21 is interposed in the coolingcircuit 180, and the relief valve 183 which is an oil-pressure riseprevention valve for bypassing the oil cooler 179. Thereby, it ispossible to cool the forward/rearward switching mechanism efficientlywith cooled oil flown through the oil cooler 179 and to keep theperformance stably.

Further, the HST 170 for steering is operatively connected with thedriving system at a position located behind the forward/rearwardswitching mechanism 21 and the main speed-change mechanism 22, and thecharge pump 17 which is a hydraulic pump for supplying servo operatingoil and charging oil to the HST 170 is operatively connected with theengine 10, whereby it is possible to stably supply the servo operatingoil and the charging oil required for the HST 170 for steering, and tokeep the performance stably.

The tractor shown in FIG. 50 has a structure in that theforward/rearward switching mechanism 21 and the gear shift mechanisms22, 23 for main and auxiliary speed change are included, and has aconventional structure in that the hydraulic steering pump 44 is drivenby the direct output from the engine 10 so as to rotate the machine bodyin a non-stepwise manner via the steering motor 45 and the forceddifferential mechanism 25, in which the conical link mechanism 72 isconnected to the reverser lever 96 for the reverser valve 99 forswitching on and off the hydraulic multiple-disc forward/rearwardclutches 97, 98 of the forward/rearward switching mechanism 21. Anauxiliary speed-change member 85 for reverser is provided on theauxiliary speed-change operating shaft 82, the operating shaft 82 isconnected to a reverser arm 184 of the reverser valve 99 via a reverserlink 185, and the reverser lever 96 is connected to an operating arm 186provided on the operating shaft 82 via a reverser shaft 187. When thereverser lever 96 is operated for forward or rearward movement, theinput fulcrum shaft 78 (bottom face angle of the bottom face 72 a of theconical link mechanism 72) is tilted at maximum (26°). In such astructure, the ratio between the steering angle of the steering wheel 18in traveling forward or rearward and the rotational speed at changingdirection or turning the vehicle is changed via the conical linkmechanism 72.

As obvious from the above, the steering pump 44 is connected to thesteering wheel 18 via the conical link mechanism 81 and the reverserlevers 96 for the travel speed-change mechanisms 22, 23 are connected tothe conical link mechanism 72, and the steering pump 44 is operated inassociation with the operation of the reverser lever 96, whereby thetractor is so set that when the machine body moves forward by theoperation of the reverser lever 96, the rotational difference betweenthe right and left crawlers 9 becomes large relative to a certainsteering amount of the steering wheel 18, and when the machine bodymoves rearward, the rotational difference between the right and leftcrawlers 9 becomes small. Thereby, the right and left traveling crawlers9 are driven with an appropriate rotational difference corresponding tothe forward/rearward operation so as to achieve good feeling intraveling forward/rearward.

FIGS. 51 and 52 show a configuration that the machine body is rotated orsteered by the hydraulic steering pump 44 and the hydraulic steeringmotor 45 of the hydrostatic transmission (HST) and the machine body ismade to travel straight by the hydraulic travel pump 188 and thehydraulic travel motor 189 of the hydrostatic transmission (HST). Bothof the steering and travel pumps 44 and 188 are driven by the output ofthe engine 10 located behind the forward/rearward switching mechanism21, while the steering and travel motors 45 and 189 are connected to thebevel gears 49 and 41. Each pump 44 or 188 and motor 45 or 189 aredisposed separately. Specifically, the steering pump 44 and the travelpump 188 are disposed in serial at a position of outside surface of thetransmission case 30, which position is behind the forward/rearwardswitching mechanism 21. The steering motor 45 and the travel motor 189are disposed opposite each other at the front and rear sides of thefront transmission case 2, and respective motors 45 and 189 are disposedopposite each other at the front and rear of the transmission case 2having the forced differential mechanism 25, and thereby the steeringmotor 45 and the travel motor 189 are mounted to the transmission case 2with the compact integrated structure so as to enable the machine bodyconfiguration to be simplified.

As obvious from the above, the hydraulic travel pump 188 and the motor189 which are the HST for travel to change the travel speed, and thesteering pump 44 and the steering motor 45 are connected to the drivingsystem at a position located behind the switching mechanism 21, and thepump 44 for travel and the pump 188 for steering are connected at aposition behind the switching mechanism 21 in a compact manner withoutlimitation so as to simplify the driving system.

Further, the travel pump 188 for hydraulically changing the travel speedand the steering pump 44 are arranged in serial so as to be formed as acompact integrated shape, which enables simple assembly into the machinebody easily. In addition, the travel pump 188 and the steering pump 44are positioned in parallel to the transmission case 30 which is adriving case, which easily enables an arrangement integrated with thetransmission case 30 such as a transmission case for transmitting enginedriving force, whereby it is possible to improve freedom in the layoutand simplification of the driving system.

As shown in FIG. 53, the tractor is so configured that a first fuel tank190 for the engine 10 is disposed between the right and left fenders 64behind the driver seat 17, and a second fuel tank 191 for the engine 10is disposed within the right fender 64 and a battery 65 is disposedwithin the left fender 64, respectively. With the first and second fueltanks 190, 191, the reserved amount of the fuel increases, and the rightand left balance of the machine body is kept in a good condition withthe second fuel tank 191 and the battery 65 placed on the opposite side.Further, the covers 192 are mounted openably/closably outside the rightand left fenders 64 so as to improve the maintainability of the secondfuel tank 191 and the battery 65. The first and second fuel tanks 190and 191 may have a configuration that fuel supply is performed through asingle oil supply port 193 formed in the first fuel tank 190 by fluidlyconnecting them at lower parts thereof, or that fuel supply is performedthrough an oil supply port 67 formed in each fuel tank 63 or 64. Notethat the tractor may have such a configuration that a third fuel tankfor the engine 10 is disposed within the left fender 64 so that thesecond and third fuel tanks 191 are disposed in right and left fenders64 with the first fuel tank 190 disposed behind the driver seat 17,whereby the driver seat 17 is surrounded by the three tanks 190, 191 soas to increase the reserved amount of the fuel.

1. A crawler tractor comprising a machine body having a left side and aright side; an engine; a left traveling crawler on the left side of themachine body; a right traveling crawler on the right side of the machinebody; a traveling speed-change mechanism interposed in a travelingtransmission path extending from the engine to the pair of travelingcrawler; a steering hydrostatic transmission for steering the machinebody; a planetary gear differential mechanism that differentially drivesthe pair of traveling crawlers, wherein the planetary gear differentialmechanism receives a traveling speed-change output from the travelingspeed-change mechanism and a steering output from the steeringhydrostatic transmission; a traveling brake capable of applying a brakeforce on the traveling transmission path; a front transmission casearranged at a front side of the machine body and accommodating thedifferential mechanism; a rear transmission case accommodating thetraveling speed-change mechanism, wherein the planetary geardifferential mechanism is operatively connected to a final output shaftof the traveling speed-change mechanism through a traveling transmissionshaft; a reverser for switching between a first direction of movementand a second direction of movement of the machine body, the reverserhaving an output side, wherein the steering hydrostatic transmission hasan input side connected downstream from the reverser mechanism along thetraveling power transmission path, downstream in the driving systemrefers to an output side, and the traveling brake is arranged at therear transmission case so as to apply the brake force on the finaloutput shaft.
 2. The crawler tractor according to claim 1, wherein thetraveling brake includes a brake shaft operatively connected to thefinal output shaft, the brake shaft supported by a side wall of the reartransmission case, and a brake case connected to the side wall.
 3. Thecrawler tractor according to claim 1, wherein the traveling brakeincludes a brake shaft operatively connected to the final output shaft,and the brake shaft having two ends, both ends of the brake shaft beingsupported by the rear transmission case.
 4. The crawler tractoraccording to claim 1, further comprising a brake case connected to theleft side of the rear transmission case with respect to the machinebody; a brake case connected to the right side of the rear transmissioncase with respect to the machine body, wherein the traveling brakeincludes a brake shaft operatively connected to the final output shaftand a brake plate supported by the brake shaft, the brake plateaccommodated in one of the pair of brake cases, wherein the left andright crawlers have crawler frames supported by the brake cases andcrawler belts mounted on the crawler frames.
 5. A crawler tractoraccording to claim 1, wherein the steering hydrostatic transmissioncomprises a steering pump and a steering motor that are arrangedseparately, the steering pump is connected to the rear transmissioncase, and the steering motor is connected to the front transmissioncase.